1. Field of the Invention
The invention relates to apparatus for reproducing information contained in tracks on a disc-shaped optically readable record carrier, and, more particularly, control of such apparatus following track loss.
2. Description of the Prior Art
In known compact disc players, the information on the tracks includes a position code which is a continuous indication of the radial position on said record carrier. The known apparatus comprises
an optical system for projecting a light beam on the record carrier, PA0 a detector arranged in the light beam which has been modulated by the information structure on the record carrier, for supplying a signal which is modulated by the information recorded on the record carrier, PA0 a radial-position control circuit for controlling the radial position of the spot formed on the record carrier by the light beam, PA0 a position-code detector for extracting said position code from the detected signal, PA0 a track-loss detector circuit for generating a signal which is indicative of the condition that the spot formed by the light beam no longer follows the track. PA0 a storage circuit for storing last time code data read at an instant immediately prior to loss of track, and PA0 means for applying a start-position code which is determined only in part by said last time code data to the radial-position control circuit for restarting the reproduction at a position which is defined by said start-position code.
Such an apparatus is commercially available in many versions as a "compact-disc-digital-audio" player, for example the player with the type number CD 100 from N. V. Philips' Gloeilampenfabrieken, as described in Philips Technical Review, Vol. 40, 1982, no. 6.
Such a player is suitable for use in motor cars, but the susceptibility to mechanical shocks and electrical disturbances in the supply voltage then poses a problem because this may give rise to loss of track.